JP2012203334A - Optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical element which reduces the number of components and suppresses manufacturing costs from being increased or convergence tolerance from being deteriorated.SOLUTION: In an optical element, two light beams (A and B) are inputted to a birefringence material 10, four output light beams comprised of normal light beams (a1 and b1) and abnormal light beams (a2 and b2) corresponding to the input light beams are outputted, and the output light beams are made incident to a light-receiving element 40 while reducing a beam diameter and narrowing a beam interval. In the optical element, in an output terminal of the birefringence material 10, optical path conversion means 20 is disposed which converts an optical path in such a manner that the four output light beams (a1, a2, b1 and b2) cross approximately at one point (chain line D) and between the crossing point and the light-receiving element 40, convergence means 30 is provided which reduces the beam diameter of each output light beam.

Description

  The present invention relates to an optical element, and more particularly to an optical element configured such that two input lights are incident on a birefringent material and four output lights composed of ordinary light and extraordinary light are incident on a light receiving element.

Polarization orthogonal multiplex multilevel modulation (Dual Polarization)
High-speed communication means exceeding 100 Gbit / s has been proposed, such as Differential Quadrature Phase Shift Keying (DP-QPSK). In optical receivers used for these optical communications, a plurality of polarization-separated output lights are incident on a light receiving element such as a photodiode, and optical signals are converted into electrical signals (O / E conversion). It has been broken.

As shown in Non-Patent Document 1, the optical coupling system in the conventional O / E converter is the planar optical circuit (Planar
A light wave (dotted line) output from a light wave circuit (PLC) 1 is introduced into the light receiving element 5 by two lens arrays 2 and 4 and a mirror (prism) 3 that turns back to 90 °.

  In the optical coupling system as shown in FIG. 1, the number of parts is large and the adjustment of the optical parts is complicated, which causes an increase in manufacturing cost. Further, due to the influence of the pitch and intersection of the lens array, the light condensing tolerance for condensing light on the light receiving element has also become strict.

T. Ohyama et al., "All-in-one100-Gbit / s DP-QPSK Coherent Receiver using Novel PLC-based Integration Structure with Low-loss and Wide-tolerance Multi-channel Optical Coupling", 15th Opto Electronics and Communications Conference (OECC2010) Technical Digest, July 2010, Sapporo Convention Center, Japan

  The problem to be solved by the present invention is to provide an optical element that solves the above-described problems, reduces the number of parts, and suppresses an increase in manufacturing cost and deterioration in light collection tolerance.

  In order to solve the above-mentioned problem, the invention according to claim 1 inputs two input lights to a birefringent material, outputs four output lights composed of ordinary light and extraordinary light corresponding to each input light, and outputs the output light. Is an optical element that enters the light receiving element in a state where the beam diameter is reduced and the beam interval is narrowed, and an optical path for changing the optical path so that the four output lights intersect at substantially one point at the output end of the birefringent material A converting means is arranged, and a condensing means for reducing the beam diameter of each output light is provided between the intersecting point and the light receiving element.

  According to a second aspect of the present invention, in the optical element according to the first aspect, the optical path changing means is composed of one optical component in which at least one of the incident surface and the emitting surface is formed of a polyhedron. And

  The invention according to claim 3 is the optical element according to claim 1 or 2, characterized in that the light condensing means is constituted by a spherical lens.

  According to a fourth aspect of the present invention, in the optical element according to the third aspect, the spherical lens is a hemispherical spherical lens, and a light wave incident from a curved surface portion of the spherical lens is reflected by a plane, and the other curved surface portion. It is comprised so that it may radiate | emit from.

  According to the first aspect of the present invention, two input lights are input to a birefringent material, four output lights composed of ordinary light and extraordinary light corresponding to each input light are output, and the beam diameter of the output light is reduced. In addition, in the optical element that is incident on the light receiving element in a state where the beam interval is narrowed, an optical path changing unit that changes the optical path so that the four output lights intersect at substantially one point is disposed at the output end of the birefringent material, Since a condensing means for reducing the beam diameter of each output light is provided between the intersecting point and the light receiving element, there are only two optical parts, an optical path changing means and a condensing means, so the number of parts is reduced. In addition, the adjustment of the optical components can be simplified, so that an increase in manufacturing cost can be suppressed. In addition, since the four output lights incident on the light receiving element are condensed by one condensing unit, it is possible to increase the condensing tolerance unlike the conventional lens array.

  According to the invention of claim 2, since the optical path changing means is composed of one optical component in which at least one of the incident surface and the exit surface is a polyhedron, the number of components is small and an increase in manufacturing cost is suppressed. It becomes possible. In addition, by adjusting the angle of the surface of the polyhedron, it is possible to adjust the beam interval of the four output lights incident on the light receiving element, and the pitch of the beam interval can be easily adjusted.

  According to the invention of claim 3, since the light condensing means is composed of a spherical lens, it becomes possible to condense four output lights with one optical component, suppressing an increase in manufacturing cost, and the entire optical element. This contributes to downsizing of the product.

  According to the invention of claim 4, the spherical lens is a hemispherical spherical lens, and the light wave incident from the curved surface portion of the spherical lens is reflected by the plane and is emitted from the other curved surface portion. In addition to condensing light, the optical path can be bent at 90 ° with a single optical component. Therefore, an increase in the manufacturing cost of the optical element can be suppressed, and the entire element can be downsized.

It is a figure explaining the outline of the conventional optical element disclosed by the nonpatent literature 1. FIG. It is a figure explaining the outline of the optical element of this invention. (A) is a plan view and (b) is a side view. It is a top view explaining the other Example of the optical element of this invention. It is a figure explaining the outline of the optical path changing means used for the optical element of FIG.

Hereinafter, the optical element of the present invention will be described in detail using preferred examples.
In the present invention, as shown in FIG. 2, two input lights (A, B) are input to the birefringent material 10, and from ordinary light (a1, b1) and extraordinary light (a2, b2) corresponding to each input light. In the optical element in which the output light is output, and the output light is incident on the light receiving element 40 in a state where the beam diameter is reduced and the beam interval is reduced, the output light of the birefringent material 10 is An optical path changing means 20 for changing the optical path is arranged so that the two output lights (a1, a2, b1, b2) intersect at substantially one point (one-dot chain line D), and between each of the intersecting points and the light receiving element 40, Condensing means 30 for reducing the beam diameter of the output light is provided.

  In the present invention, “intersecting at approximately one point” is not limited to the technical scope of the present invention being “intersecting at one point”, but may be slightly deviated from the one point within the scope of the effects of the present invention. Means good.

  As the birefringent material, yttrium vanadate (YVO4) can be used. It is possible to adjust the separation state and propagation direction of ordinary light and extraordinary light by interposing a 45 ° half-wave plate between two birefringent materials. In a birefringent material, since the refractive index differs depending on the polarization direction of the light beam passing through the crystal, the optical distance (refractive index × propagation distance in the material) of the light beam passing through the crystal differs for each polarization direction. For this reason, as shown in FIG. 2, the birefringent material crystal 10 is divided into two parts, a first half and a second half, and the polarization direction of each light beam passes through the crystal by rotating the first half and the second half by 90 °. The optical distance of all the light rays to be made is the same. Further, a half-wave plate 11 is inserted between the crystals in order to rotate the polarization direction of the light beam by 90 ° between the first half and the second half of the crystal.

  In FIG. 2, a 45 ° half-wave plate 11 is interposed between the two birefringent materials 10 for the reason described above. However, the present invention is not limited to this, and as shown in FIG. In addition, an optical path length adjusting plate 12 such as a glass plate may be disposed immediately after the first birefringence material 10 and the second birefringence material may be omitted.

  After the birefringent material 10 separates the four output lights (a1, a2, b1, b2), the optical path conversion means adjusts the optical path of each output light, and the four output lights are indicated by a one-dot chain line D. Set to intersect at As shown in FIG. 4, the optical path changing means 20 is composed of one optical component in which the incident surface 21 has a surface parallel to the exit surface of the birefringent material, and the exit surface is composed of polyhedrons 22 to 25. ing.

  By making the incident surface 21 of the optical path changing means parallel to the exit surface of the birefringent material, the birefringent material and the optical path changing means can be integrated with high accuracy, so the position and angle of each optical component can be adjusted. It is not necessary to adjust and a simple configuration can improve reliability. The optical path changing means can be configured not only to make the exit surface a polyhedron but also to make the incident surface a polyhedron.

  By adjusting the angles θ1 to θ4 of the respective faces of the polyhedrons 22 to 25 constituting the optical path changing means, it is possible to change the beam interval (pitch) incident on the light receiving element 40. In the present embodiment, the four output lights intersect at the position indicated by the alternate long and short dash line D. The position of the intersection of the output lights depends on the optical diameter and the beam position of the light receiving element to be incident thereafter. It is permissible if it does not affect the range. That is, the four output lights may intersect at substantially one point. Further, the polyhedron only needs to be formed on at least one of the incident surface and the exit surface of the optical path changing means as long as it has a function of intersecting the four output lights at approximately one point.

  The light condensing means can be composed of a spherical lens. By arranging so that the curved surface of the spherical lens is positioned at the position indicated by the alternate long and short dash line D, it is possible to condense the beam diameter of the output light using the spherical lens. In addition, since the light is collected by one lens, the light collection tolerance can be improved.

  In the optical element of the present invention, a hemispherical spherical lens is used as the condensing means 30 as a concentrating spherical lens as shown in FIG. With this configuration, as shown in FIG. 2B, the light wave incident from the curved surface portion of the spherical lens can be reflected by the plane and emitted from the other curved surface portion, and the optical path can be bent at 90 °. It becomes possible. Normally, the light receiving surface of the light receiving element is arranged in a state facing the perpendicular direction of the plane on which the birefringent material is arranged in consideration of the electronic wiring around the light receiving element, but light can be easily obtained by bending the optical path to 90 °. Can be incident on the light receiving surface, and the arrangement and adjustment of optical components can be facilitated.

  In the optical element as shown in FIG. 2, for example, when the beam diameter of the output light emitted from the birefringent material is 0.8 mm and the beam interval is 1.0 mm, the intersection from the emission position C of the optical path changing means 20 By using an optical path changing means such that the distance to D is 8 mm, and using the diameter φ4 mm of a hemispherical sphere lens as the condensing means 30, the beam diameter can be adjusted to 10 μm and the beam interval to 250 μm. It becomes possible.

  As described above, according to the present invention, it is possible to provide an optical element in which the number of parts is reduced and an increase in manufacturing cost and deterioration in light collection tolerance are suppressed.

DESCRIPTION OF SYMBOLS 10 Birefringent material 11 45 degree half-wave plate 12 Optical path length adjusting plate 20 Optical path conversion means 30 Condensing means 40 Light receiving element

Claims (4)

Two input lights are input to a birefringent material, and four output lights composed of ordinary light and extraordinary light corresponding to each input light are output, and the beam diameter of the output light is reduced and the beam interval is reduced. In the optical element to be incident on the light receiving element in
An optical path changing means for changing the optical path is arranged at the output end of the birefringent material so that the four output lights intersect at approximately one point, and the beam diameter of each output light is between the intersecting point and the light receiving element. An optical element, characterized in that a light condensing means for restricting the aperture is provided.   2. The optical element according to claim 1, wherein the optical path changing means has one surface in which an incident surface has a plane parallel to the exit surface of the birefringent material, and at least one of the entrance surface or the exit surface is a polyhedron. An optical element comprising an optical component.   The optical element according to claim 1, wherein the light condensing means is constituted by a spherical lens.   4. The optical element according to claim 3, wherein the spherical lens is a hemispherical spherical lens, and a light wave incident from a curved surface portion of the spherical lens is reflected by a plane and emitted from another curved surface portion. An optical element.

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